Check car seat, finally (5)
I believe the answer is:
audit
'check' is the definition.
(an audit is an examination or check)
'car seat finally' is the wordplay.
'car' becomes 'audi' (Audi is a German car brand).
'finally' indicates one should take the final letters.
The final letter of 'seat' is 't'.
'audi'+'t'='AUDIT'
(Other definitions for audit that I've seen before include "Investigate" , "vetting of books" , "Roman Aquae Sulis" , "Stocktake" , "Financial review" .)